1. Field of the Invention
The present invention relates to a hermetic electric scroll compressor for compressing fluid, such as air or refrigerant gas.
2. Description of the Prior Art
As shown in FIG. 5, a hermetic electric scroll compressor includes, in a sealed casing 101, an electric motor 102 and a compression unit 105 driven by the electric motor 102 whose rotation force is transmitted to the compression unit 105 via a crankshaft 104 rotatably supported by a support member 103. The compression unit 105 includes a fixed scroll 106 having a spiral vane and an orbiting scroll 107 having a spiral vane which is interfitted or mated with the spiral vane of the fixed scroll 106 to define therebetween a plurality of compression spaces 109. The orbiting scroll 107 is prevented from rotation on its axis by an Oldham's ring 108 interposed between the orbiting scroll 107 and the support member 103, while it makes a swing motion or an orbital motion depending on the rotation of the crankshaft 104. The orbital motion of the orbiting scroll 107 causes the compression spaces 109 formed between the spiral vanes of the fixed and orbital scrolls 106 and 107 to move toward the center and reduce their volumes to thereby compress the introduced fluid. In the scroll compressor of this type, the compression efficiency is improved by reducing leakage of the fluid through between contact surfaces of the spiral vanes of the scrolls defining the compression spaces. For reducing the fluid leakage, the technique has been known to introduce lubricating oil stored in the sealed casing 101 into the compression spaces 109 so as to seal them using oil films of the introduced lubricating oil.
In the conventional scroll compressor, the lubricating oil drawn up by a pump passes through the inside of the crankshaft 104, then a portion of the lubricating oil is fed to an eccentric bearing 111 and a bearing 110, while the other portion of the lubricating oil passes through a communication hole 112 formed in a shaft portion and a base plate of the orbiting scroll 107 and then adequate amounts of the lubricating oil are fed to the compression spaces 109 via a restrictor 113, as shown in FIG. 6, disposed in the base plate of the orbiting scroll 107.
In the foregoing scroll compressor, it is necessary to incorporate the restrictor 113, as a separate member, into the orbiting scroll 107. This results in additional manufacturing cost and additional assembling step of the restrictor 113. Further, owing to a difference in thermal expansion coefficient between the restrictor 113 and the orbiting scroll 107, the lubricating oil exceeding the adequate amounts may flow into the compression spaces 109 due to temperature increase during operation of the compressor. This lowers the compression efficiency of the compressor.
Further, key portions of the Oldham's ring 108 and corresponding key grooves of the orbiting scroll 107 which slidably receive therein the key portions of the Oldham's ring 108 are in a boundary lubrication state so that, if the lubricating oil supplied thereto becomes insufficient, the key portions of the Oldham's ring 108 and the key grooves of the orbiting scroll 107 may be subjected to abnormal abrasion, thereby lowering the mechanical efficiency.
Further, since the communication hole 112 has an outlet only in one direction, the uniform supply of the lubricating oil is difficult to cause insufficient sealing of the compression spaces 109.